1. Field of the Invention
The present invention relates to a method and to an apparatus for polishing a roller, particularly a gravure roller, and for removing the chromium plating thereof.
2. Description of the Prior Art
A gravure roller is generally made of a steel cylinder covered with a copper layer on which a pattern or drawing can be impressed. A chromium protective covering is subsequently applied to the copper layer. The gravure roller is then ready to be used for reproducing the pattern or drawing on a sheet of paper.
When the printing operation is completed, the pattern or drawing has to be eliminated from the gravure roller. As well known in the art, such operation is very difficult and time consuming. The operation of eliminating the pattern from the gravure roller consists of a first step of removing the chromium plating by electrical treatment and a second step of working the copper layer with special machines in order to remove the pattern from it.
This prior art method has the disadvantage of requiring the use of very expensive machines and of requiring long working cycles because of the set up time necessary to move the cylinders from the galvanic chromium plating removal apparatus to the machine tools for removing the pattern from the copper layer.
On the other hand, instead of the removing the protective chromium plating by a galvanic treatment, other systems are known which use lathe--smoothing machines which turn the cylinder and at the same time remove the chromium plating and the pattern on the copper layer. After the removal of the pattern the copper layer has to be smoothed. Such method, which is indeed rarely used, requires cheaper equipment than the above described method but also requires longer working times.